If either of the above apps aren’t your default, you might need to change that. Right now, you can only block a number if it’s able to write to Android’s master block list and if that app is set as your default. As of this writing, we know that Google’s Dialer and Messenger apps can do that. However, if they’re not set to your default, the menu options to block numbers will disappear. To change the default back, follow these steps:
  1. Open Settings > Apps
  2. Tap the gear icon at the top of the screen
  3. Tap either Phone or SMS to change the default you want.
  4. Choose a new default from the list.
By the time most people receive Nougat, this step should become unnecessary. As long as an app supports the ability to write to the block list and it’s set to your default, you should have the option somewhere in your menus. However, if you don’t see it, just change your default to one of these apps.

For now, Nougat’s number blocking is a little more complicated than it needs to be. According to Google’s developer notes, if you want to block a number, you’ll need to do it in either the default phone app, the default SMS app, or certain carrier apps. That means each phone and SMS app needs to be updated both to read the new master block list to know which numbers to block, and to be able to write to the list if they’re set as the default.
Nougat will take a while to roll out to most phones and by the time that happens, your favorite phone and SMS apps will probably support this feature. For now, though, you have to jump through a couple small hoops to make it work. Still, it’s way easier than having to block a number in every app you use.